Balancing a 360 internally

it's extremely common on race engines that will see large amounts of RPM. personally i paid about $300 to have mine balanced. I run a trickflow neutral balance balancer, and needed a flywheel for internal balance. but i make 650 HP and turn 7300 RPM...long story short, if you're reusing a stock crank, just throwing some pistons in it to bump compression and add a few ponies...stick with external. You won't see enough benefit from the switchover to make it worth doing.